Action and Mechanism of Epstein Barr virus Latent Membrane Protein1 induced Immortalization of Mouse Embryonic Fibroblasts

To investigate the action and mechanisms of Epstein Barr-virus(EBV) latent membrane protein1(LMP1) in stimulating the proliferation of primary mouse embryonic fibroblast (MEF) cells the retrovirus (RV) containing wild type LMP1(wt-LMP1) and mutant type LMP1(mt-LMP1);which replaced YYD with ID in tumor necrosis factor receptor associated death domain(TRADD)-binding site;were constructed and used to infect the MEF cells;respectively. Then cytokinetic and morphologic changes from infected cells at the course of passage were observed and found that control cells (MEF-LNSX) showed an apparent growth arrest from passages 8 (P8). In contrast;mt-LMP1 prolonged the cell (MEF-LMP1TRADD) doubling time since P10 and arrested growth at P19;while the MEF-LMP1 cell with wt-LMP1 had an accurate doubling time and displayed a immortalization. Meantime;the expression of cyclinA had a decrease in MEF-LNSX and MEF-LMP1TRADD after P4and P10 respectively. while in MEF-LMP1;cyclinA increased from P10 and kept at a high level. These results suggested that LMP1 can stimulate proliferation of MEF cells and induce their immortalization;while LMP1TRADD only induces an early proliferation of MEF cells. It is implied that TRADD domain might involve in LMP1-induced MEF cells immortalization.